Field of Invention
The present disclosure relates to a method for generating injection current for a fuel cell stack and an apparatus for performing the same.
Description of Related Art
A fuel cell is a kind of a power generating device which does not convert the chemical energy of a fuel into heat by combustion but converts the chemical energy into electrical energy by an electrochemical reaction in a stack, and may be used to not only supply industrial power, home power and vehicle driving power but also supply power to a small electric/electronic product, particularly, a portable device.
As a power supply source for driving a vehicle, a polymer electrolyte membrane fuel cell (PEMFC) (a proton exchange membrane fuel cell) having the highest power density among fuel cells has been currently studied mainly. The polymer electrolyte membrane fuel cell has a rapid start time and a rapid power converting reaction time due to a low operation temperature.
The polymer electrolyte membrane fuel cell is configured to include a membrane electrode assembly (MEA) in which catalyst electrode layers in which electrochemical reactions occur are attached to both sides of a solid polymer electrolyte membrane through which hydrogen ions pass, gas diffusion layers (GDL) which serve to uniformly distribute reaction gases and transfer generated electrical energy, gaskets and coupling mechanisms which maintain airtightness of the reaction gases and a coolant and an appropriate coupling pressure, and bipolar plates which move the reaction gases and the coolant.
When a fuel cell stack is assembled using the configuration of a unit cell as described above, the combination of the membrane electrode assembly and the gas diffusion layers, which are main parts, is positioned in the innermost portion of the cell. The membrane electrode assembly has the catalyst electrode layers applied with catalysts to allow hydrogen and oxygen to react with each other, that is, an anode and a cathode, on both surfaces of the polymer electrolyte membrane, and the gas diffusion layers, the gaskets, and so forth are stacked on the outer sides of the anode and the cathode.
The bipolar plates formed with flow fields, through which the reaction gases (hydrogen as a fuel and oxygen or air as an oxidizer) are supplied and the coolant passes, are positioned on the outer sides of the gas diffusion layers. After a plurality of unit cells each having the above-mentioned configuration are stacked, current collectors, insulating plates, and end plates for supporting the stacked cells are coupled to outermost portions. The fuel cell stack is configured by repeatedly stacking and coupling the unit cells between the end plates.
In order to obtain the potential actually required in a vehicle, unit cells should be stacked to correspond to the required potential, and the structure formed by stacking the unit cells is referred to as a stack. The potential generated by one unit cell is about 1.3V. Therefore, in order to generate the power required for driving a vehicle, a plurality of cells are stacked in series.